New X-ray Irradiation Used to Sterilize Diplomas


The 2020 commencement ceremony of Chulalongkorn University saw, for the first time in Thailand, the application of x-ray irradiation sterilization technology to sanitize all the diplomas before being conferred to graduates. The process was carried out as a precaution against the spread of COVID–19 and the mitigation of pathogenic bacteria.

The x-ray irradiation sterilization process was conducted as a collaboration between Chulalongkorn University’s Registrar’s Office; M3D laboratory, Chula Engineering; Thailand Institute of Nuclear Technology (TINT); and Meticuly Co., Ltd.  Diplomas were placed in boxes, loaded on a conveyor belt, then disinfected with X-ray at the National Institute of Nuclear Technology.

X-ray is a high-energy electromagnetic wave that penetrates through thick objects.  One way to produce an X-ray is to generate and accelerate electrons at high speed before hitting a specific target.  X-ray irradiation, applied at a proper dose (10 kilograys/KGy), can kill pathogenic viruses and bacteria because the radiation causes a biological alteration in the germs’ DNA.  Irradiation is an effective germicide with no residue and is a one-step process.

Mr. Torlap Sitthivanich and Ms. Sukanya Potiviput, the researchers under the supervision of Asst. Prof. Dr. Bunyarat Lohwongwatana, Head of the M3D Laboratory, Chula’s Faculty of Engineering, said that x-ray is capable of destroying the genetic materials of pathogenic viruses and bacteria.

The technology is generally used to sanitize medical devices and make them aseptic, as well as extend the shelf life of food for export.  The project received advice on the appropriate radiation dosage from Mrs. Nongnuch Chaengsawang, Head of Radiation Center Development and Services, Thailand Institute of Nuclear Technology in Radiation Services.

The research team conducted experiments to confirm the effectiveness of x-ray sterilization in comparable bacteria that were more resistant to radiation than the COVID-19 virus.  The team also tested the effects of radiation on the paper color and ink on the diplomas with the CIE Lab technique.

Results showed that the color change was not noticeable to the naked eye; therefore, it was concluded that x-ray irradiation can be used to effectively eradicate germs, without affecting the material or color of surfaces.